Process of molding.



" Processes of Molding, of which thefollow- To all whom it'may concern iii-ES P. 'h. McCOY, E WILKINSBURG, PENNSYLVANIA, ASSIGNOB TO WESTINGHOUSE ELECTRIC AND MANUFNOTURING- COMPANY, A. CORPORATION 015 PENNSYLVANIA.

PROCESS OF MOLDING.

Be it known that I, JAMES P. A. MCCOY, a subject of the King of Great Britain, and a resident of Wilkinsburg, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in ing is a specification.

My invention relates to molding processes, and it has special reference to processes that are adapted to the manufacture of'molded electrical insulation.

The objects of my invention are to prepare novel, efiective and inexpensive materials of high insulating efficiency and to mold such materials into shapes without the applica will absorb a small quantity of the solvent and the particles of the resin will swell and soften slightly. This slight swelling and softening are suflicient to enable the material to be compressed into a coherent mass, the

particles of the material being apparently. welded or knit together under pressure.

Only a very small amount of solvent is i needed, preferably. only enough to efiect the swelling and softening just described without actually wetting the powder, which,

I after treatment with the solvent, 'may still be pulverulent and dry to the touch. However, under the pressures commonly employedin manufacturing .molded shapes from plastic material, the powder will cohere perfectly and yield highly satisfactory molded articles. On account of the small quantity of solvent that is present, the

shrinkage upon molding is exceedingly low.

It is usually desirable to mix with the resin, or other binder under treatment, 'a suitable quantity ofinert filler, such as finely divided asbestos or wood flour, as is com? Specification or Letters Patent.

. I Patented Dec. 3, llfi l.

Applicationfiled m a, 191i. Serial No. states. y

I monly done when molding with the compositions heretofore employed.

My process may be applied to a wide variety of binders and solvents, and I. do not desire to .be restricted to the use of insoluble binding substances, such as the bakelite or wurtzilite referred to above, since soluble binders are equally applicable for use in my process. The use of .soluble binders may often be preferable, since'a smaller amount of binder, in proportion to the filler present, is necessary to form the molded articles than when the binder is insoluble.

After the molded articles are pressed in the cold, the small amount of solvent present inthe molded articles will be found to be near the surface, and can be wholly expelled by sub ecting the molded articles to a -gentle heat for a short time.

The nature and amount of solvent to be added to the powdered binder and filler vary, of course, according to the nature of the binder, and according 'to whether the solvent actually dissolves the binder or only has the efiect of causing it to swell and soften. The proper amount of solvent to be used must be determined in each case, which may conveniently be done by mixing a small portion of the powder with the solvent and adding small amounts of each, with constant agitation, until the mass assumes a powdered condition and is. free from lumps. The binder may be applied as a spray of liquid or, if'it is of a readily vaporizablenature, it is preferable to apply itin the form of vapor, in which case the mixture of the pulverized solvent and filler may conveniently be'tumbled in a ball mill to which vapors of the solvent are supplied.

- In carrying out my process with a specific binder, that solvent should be selected to the action of which the given binder is most susceptible. Thus, I prefer to, use benzol as the solvent when coal-tar pitch is the binder, and. methyl alcohol when shellac is the binder, while for bakelite, ll prefer to usea mixture of benzol and methyl alcohol.

According to one modification of my invention, ll prepare cold-molded articles with coal tar pitch as the binder, The coal tar pitch is first heated at about 260 or 300 0., in order to expel its easily volatile constituents. It is then pulverized, mixed with any suitable filler, moistened with a small other than those indicated in the amount of solvent in the manner described above, and molded in the cold. Any of the well known solvents may be employed inconnection with coal tar pitch, but at pres-- ent, I prefer to use benzol as the solvent and to apply it in the form of vapor, While the pulverized pitch and filler are tumbled in a ball mill.

In the subjoined claims, the expression resinous substance is to be understood as a generic term,-including all resins, gums, gum-resins, synthetic resins, pitches, tannins, and all other substances, whether soluble or insoluble, that can be used as binders in the preparation of plastic compositions.

The examples and substances which I have mentioned are intended to be merely illustrative, and numerous other applications of my process will readily suggest themselves to persons skilled in the art; It is to be understood, therefore, that my invention comprehends broadly all processes in which a discrete substance is caused to cohere by the addition ofa small amount of liquid, which affects it either as a solvent or only as *a swelling and softening agent. Itis also to be understood that no limitations are to be imposed upon my invention claims.

I claim as myinvention: 1. A' process of molding that comprises heating a resinous substance to drive off any soften, and subjecting the resulting mass to 7 pressure.

3. A process of molding that comprises appended I heating a pitch to drive off its easily volatile constituents, finely-dividing the residue, treating the said finely-divided residue with a liquid capable of causing it to swell and soften, the amount of said liquid being sufficient to swell and soften the said residue without wetting it, and subjecting the resulting mass tov pressure.

4. A process of molding that comprises heating coal tar pitch to drive off its easily volatile constituents, finely-dividing the residue, treating the said finely-divided residue with a liquid capable of causing the said residue to swell and soften, and subjecting due, treating the'said finely-divided residue with benzol and subjecting the resulting mass to pressure.

7. A process of molding that comprises heating coal tar pitch to drive off its easily volatile constituents, finely-dividing the residue, treating the resulting powder with vapors of benzol until the particles composing the powder are swelled and softened but not wetted, and subjecting the resulting mass to pressure.

In testimony whereof I have hereunto subscribed my name this 30th day of June, 1914.

JAMES P. A. MCCOY. Witnesses:

W. H. KEMr'roN, B. B. HINES. 

